Film stretching device



NOV. 30, 1937. 5, HANSEN ET A 2,100,802

FILM STRETCHING DEVICE Filed Oct. 18, 1935 Patented Nov. 30, 1937 2,100,302

UNITED STATES PATENT OFFICE FILM STRETCHIN G DEVICE Sven Severinlhnsen and Terrence Max" Emil Wendt, Raunnda, Sweden Application October 18,1935, Serial No, 45,876

In Sweden October 22, 1934 10 Claims. (01. 271-23) The present invention relates to a stretching ing members from effecting displacement of the device for films, particularly sound films or comfilm portion on the drum. bined sound and picture films, and is applicable to Some suitable embodiments of the stretching apparatus reproducing or recording sound or device according to the present invention are sound and pictures in combination. When travshown diagrammatically in the accompanying 5 elling from a take-01f drum to a take-up drum in drawing inwhich apparatus of said type the film passes a light Fig. 1 is a side elevation of an embodiment of aperture (for exposing or recording purposes) the invention in which the support for the film and is at the same time subjected to a tensioning stretching members is movable in all directions 19 stress. In some known apparatus said tensioning within certain limits, stress has been effected by providing at each side Fig. 2 is a fragmentary side elevation of an of the light aperture stretching rolls which are arrangement in which the support for the film pressed against the film independently of each stretching members is pivoted at a fixed poin other, thus keeping it under a certain tension. and

However, such stretching means have in prac- Fig.3 is a similar fragmentary side elevation of 15 tlce been found to cause certain disadvantages, an embodiment in which the support for the film since they begin easily to oscillate which causes stretching members is guided for rectilinear mospeed variations of the film motion at the extion. posingor recording aperture. The oscillatory The film l coming from a take-off drum as in 0 motion which causes such speed variations is not an ordinary apparatus of the kind referred to the normal movement of the stretching means above passes in the direction of the arrow 2 over as a result of a change in the film tension, but driving rollers 3 and 4 and a guiding drum 5 to is an inadvertent motion, hereinafter termed an a take-up drum. The film is exposed by a beam oscillatory motion, that causes a change in the of light I entering through an aperture 6, corfilm. tension. For instance when reproducing responding to the sound to be recorded. Between 25 sound which has been correctly recorded, this the driving rollers! and 4 and the guiding drum speed variation of the film motion is attended 5, thefilmis carried according to the invention by with variations of the pitch of tone which disturbs a couple of guide rollers 8, 9, I0, I I and l2, [8, ll. the reproducing to a great extent. l5 respectively. The rollers 8 and I5 are mounted The object of the invention is to avoid the dison a movable plate It, and the rollers 9-" are 30 advantage referred to and to provide a stretching Journalled on the frame of the film exp sing aD- device which has the stretching element so reparatus. lated that an oscillatory motion causes no speed In the embodiment according to Figure 1 the variations in the film motion at the exposing or plate It is movable in all directions within the as e p re. limits determined by a circular bore l1 therein According to one essential feature of the inand a pin l8 secured to a supporting arm I! pivvention said object is attained by providing beoted at 20. A spring 2| connects the plate It at tween the stretching members eilecting the tenthe centre of its forward edge with the carryin sion a connection adapted to couple the stretcharm l9, thus applying a certain tension on the ing members .together so as to equalize tension film by way of the plate It and the rollers 8 and 4 variations occurring in the film at opposite sides i5. Two springs 22 and 23 actuate the arm at of the aperture upon oscillatory motion of the opposite sides thereof so as to keep it in a central stretching members. The connection may be position as shown. mechanical or of any other type adapted to The plate I6 is thus free to rock about the serve the purpose. The stretching members are pin it, and the plate l6 and arm l9 are free to 45 suitably yielding and mounted in spaced relaturn about the pivot pin 20 in such manner as tion to the guiding drum over which the film is may be necessary to maintain a constant tenmoved past the exposing or reproducing aperture, sionin the film. This motion for equalizing the so that the film portion situated between the tension may set up an oscillatory motion which stretching members and the guiding drum must does not, however, substantially afiect the film so be carried over a couple of guide rollers. As a tension. If the carrying. arm l9 should start result a further advantage will be attained in that an oscillatory excursion in a clockwise direction, the film portion located on the guiding drum is i. e. an inadvertent movement whi is not kept rather tight adjacent to the drum so as to quired to maintain the same tension in the upper ll preyent great oscillations of the yielding stretchand the lower sectionsv of the film, the immedl- 2 aioasoa ate result will be a decrease in the tension of the film adjacent the guide roller 55, but this decrease in tension is equalized by a similar decrease in the tension of the film adjacent the guide roller 8. This compensating effect follows pivot 20, it is obvious that the tension will be Y decreased equally in the opposed sections of the film. An oscillatory motion of plate 16 in a clockwise direction tends to decrease the tension in the fihn adjacent guide roller l5, but this compensating motion takes place immediately as the forces acting onthe carrying arm,

iii are unbalanced and the entire stretching system turns in a counterclockwise direction about the pivot 20 to effect a similar decrease in the tension at the film where it passes about the guide roller 8. It will thus be seen that the stretching members maintain the desired tension in the film under normal conditions and that inadvertent momentary oscillations do not result in unequal tensions in the film at opposite sides of the guide member 5. The speed of the film is not afiected by the oscillatory movements ,of the stretching members.

In the form of construction shown in Figure 2 the plate l6 carrying the rollers 8 and I5 is pivoted at 25 at one end, the other end being actuated by'the spring 26 tending to move the plate towards an abutment 21. The plate I6 is cut out at 28 so as. to be able to oscillate without touching the roller I4 or its pin.

The device shown in Figure 3 differs from that of Figure 2 by having the plate l6 carrying the rollers 8 and I5 mounted displaceably instead of pivotally. To this end the plate l6 has a slit 30 accommodating two guide pins 3| and 32. The plate is actuated in the direction towards the uiding drum 5 by a spring 33.

' The stretching apparatus proposed above may also be utilized as a safety member in that they may be adapted to disengage the motor for the film automatically, as for instance if the film breaks. To this effect some of the abutting pins as for instance 21 or 3| may be mounted yieldingly and be connected to a releasing device not shown for the motor.

Furthermore, to secure a movement of the film being as uniform as possible all guiding rollers, driving rollers and so on are mounted in a symmetrical relation to the optical axis, i. e. an axis coinciding with the arrow 1'. As a result the most sensible portion of the film, i. e. the portion opposite to the point of the arrow 1, will be pulled uniformly past the aperture 6. The device proposed may be used not only in connection with the sound record as assumed inthe examples described above but also at the sound reproducing. In the latter case for instance a source of light or possibly a lens system may be provided within the guiding drum 5 which is then made from transparent material.

The invention is not limited to the details shown and described by way of example, modi--- fications being possible within the scope pointed out in the appended claims.

What weclaim is:-

1. In astretching'device for films, Particularly sound films or such films in combination with picture films, means defining a light aperture, means to move the film past said aperture, stretching members at both sides of said aperture, and means to equalize film tension variations caused by oscillations of the stretching members, said equalizing means including means connecting the stretching member at one side of the aperture to the stretching member at the other side thereof.

2. In a stretching device for films, particularly sound films or such films in combination with picture films, means defining a light aperture, means to move the film past said aperture, yielding stretching members at both sides of said aperture, and means including an element connecting the stretching members at opposite sides of the aperture to equalize film tension variations caused by'oscillations of the stretching members.

3. In a stretching device for films, particularly sound films or such films in combination with picture films, means defining a light aperture, means to move the film past saidaperture, yielding stretching members mounted at' a considerable distance from said aperture at both sides thereof, and means to equalize film tension varisides thereof, a plurality of guide rollers arranged between said stretching members and said drum, and means to equalize film tension variations caused by oscillations of the stretching members, said equalizing means including means connecting the stretching member at one side-of the aperture to the stretching member at the other side thereof.

5. In a stretching device for films, particularly sound films or such films in combination with picture films, a drum and means defining a light aperture, driving rollers at each side of said drum to move the film past said aperture and over said drum, yielding stretching members and guide rollers for the film, said driving rollers, stretching members and guide rollers at one side of the aperture being symmetrically positioned relatively to said driving rollers, stretching members and guide rollers at the other side thereof, and means to equalize film tension variations caused by oscillations of the stretching members, said equalizing means including'means connecting the stretching member at one side of the aperture to the stretching member at the other side thereof.

6. In a stretching device for films, particularly sound films or such films in combination with '7. In a film" stretching device according to' claim 6, wherein the carrier consists of a plate, and means supporting said plate for free movement in all directions within determined-limits.

8. In, a. film stretching device according to 10. A film stretching device according to claim claim 6, wherein the carrier comprises a. plate 6 in combination with means controlled by said pivoted to a. fixed point. carrier for interrupting the drive to said driving 9. A film stretching device according to claim. rollers. 5 6 wherein means is provided for guiding the car- SVEN SEVERIN HANSEN. 5

tier rectllinearly. 'I'ERRENCE MAX EMJL WENDT. 

